This invention relates to photographic filmstrip processing equipment and the like wherein an advancing filmstrip has been notched at intervals along an edge or has been provided with other interval markings for the purpose of controlling operation of a cutter or other processing device in precise relation to successive advancements of the filmstrip. The invention is herein illustratively described by reference to its presently preferred form and application; however, it will be recognized that certain modifications and changes therein with respect to details may be made without departing from the essential features involved.
Commercially used filmstrip edge notching equipment is reliably precise in positioning the notches correctly in relation to the intended cutting lines or other points of reference along the filmstrip. However, a considerably lesser degree of precision is encountered in sensing and utilizing those notches for controlling the cutter or other operating mechanism accurately as a function of filmstrip position. This difficulty is due to primarily two interrelated factors: (1) imprecision in aligning the longitudinal edges of successive customer lengths of filmstrip spliced together end to end to be wound cumulatively upon the feed reel, and (2) tolerance or free play allowed in the filmstrip feeding and guiding mechanism to accommodate such misalignments. For both of these reasons the notch edge sensing device employed in the mechanism may be caused to trigger operation of the cutter or other means with incorrect timing. This may be seen from the fact that the notches or other locating elements cut in the filmstrip taper or otherwise vary in width transversely of the filmstrip. Thus, filmstrip feed travel distance between the center line of the notch (transverse to the filmstrip) and its trailing and/or leading edges (passage of which is sensed by the sensor device) can vary. Thus, if the filmstrip shifts transversely in one direction relative to the tracking point of the sensor device, the latter produces a notch leading edge signal earlier in relation to filmstrip position than if the lateral shift occurs in the opposite sense.
The present invention deals with the foregoing and similar or related problems by so processing the sensed notch edge signals that timing of the resultant trigger pulse for the cutter or other operating device is reliably accurate in relation to notch center line independently of filmstrip splicing misalignments or transerse shifting in the processing equipment.
A further objective hereof is to devise a means to that end which will operate compatibly and with digital accuracy in conjunction with a stepping motor filmstrip feed and associated pulse operated devices in a composite commercial camera filmstrip processor.
Another object is to provide a relatively simple and inexpensive yet highly reliable means by which to initiate or otherwise control the positionally related functioning of apparatus or of a process step on the basis of the imaginary center line of a notch or other indexing cut or mark formed symmetrically about that center line.